Abstract

Concepts for the final disposal of radioactive wastes are abstract models based upon available basic research data and known technology. The geosciences play a major role in their development because most involve deep burial below the biospere as well as estimates of the future effects of geological processes over long periods of time (10 3-10 6 yr). Disposal concepts are best classified for geological discussion according to two criteria: type of waste and regional significance. Waste type determines the volume of material to be treated and the necessary Containment times, and leads to (1) concepts for low-active waste (LAW) without alpha-emitters (large volume, Containment time ⇐ 10 3 yr) and (2) concepts for high-active waste containing long lived alpha-emitting isotopes (small volume, containment time 10 5-10 6 yr). Regional significance defines the organisational framework and leads to (A) concepts of burial in the continental crust within national boundaries (strongly dependent on local geological conditions) and (B) concepts of disposal in unpopulated, biologically inactive areas on an international basis (directed by global geoscientific considerations). A2 and B2 concepts present the greatest difficulties in attempts to turn them into research and development programmes and pilot projects which are both politically acceptable and scientifically sound. Consideration of A2 concepts shows the complicated factors and value judgments involved in assessing the suitability of different host rocks (salt, anhydrite, argillaceous rocks, granite, basalt, tuff). The "Earth science technical plan for mined geologic disposal of radioactive waste" of the U. S. Dept. of Energy is the most advanced attempt to put R and D in this direction on a coordinated, scientific basis within a logical framework. The only B2 concept which has developed into an international R and D programme is that of disposal in ocean floor Sediments at mid-plate, mid-gyre locations. The present "Seabed disposal program", under U. S. leadership, is carrying out extensive studies and in situ tests in the deep ocean floor of the North Pacific and other localities.